Relation between hydration status in children and their dietary profile - results from the DONALD study.

OBJECTIVE: To describe associations between hydration status and dietary behaviour in children, as current research indicates that hydration status is influenced by nutrition vice versa, hydration status may influence dietary behaviour. DESIGN: Cross-sectional analyses of data from the Dortmund Nutritional and Anthropometric Longitudinally Designed Study, (DONALD) using 24-h urine samples to determine the hydration status and 3-day weighed food records to describe the dietary profile of the children. SETTING: Secondary analyses of data from an observational study. SUBJECTS: A group of 4-11 year old children living in Dortmund, Germany; N=717. METHODS: Hydration status was determined by calculating the 'free water reserve', using analyses of the 24-h urine samples. Nutrient intake per day was calculated from the 3-day weighed food records. Children were categorized into groups of hydration status and analysed for significant differences in their dietary profile. RESULTS: Children in the highest group of the hydration status had significant higher total water intake, lower energy density of the diet and a lower proportion of metabolic water compared to children in the lowest group of the hydration status. In addition, analyses showed - although not significant in all subgroups - that better hydrated children consumed more water from beverages and water-supplying foods and less energy from fat. CONCLUSIONS: Euhydrated children, that are children in the highest group of hydration status, had a more preferable dietary profile than children at risk of insufficient hydration. SPONSORSHIP: Funding for the DONALD Study and its analyses is provided by the Ministry of Innovation, Science, Research and Technology of the State of North Rhine-Westphalia, Germany.

The muscle-bone unit in adulthood: influence of sex, height, age and gynecological history on the bone mineral content and muscle cross-sectional area.

Bone and muscle development are both strongly influenced by sex hormones. The purpose of this study was to examine the changes in bone and muscle parameters (bone mineral content - BMC, muscle cross-sectional area - MA) in 130 men aged 31 -60 years, and in 180 pre-menopausal women aged 30-53 years with respect to age, body height and, with the women, their gynecological history (age-at-menarche, number of pregnancies, duration of lactation and use of oral contraception). The study was performed using peripheral quantitative computed tomography (pQCT) at a 65% site of the forearm length. Both BMC and MA were dependent on body height (p<0.0001), but not on age. The BMC/MA ratio was dependent neither on age nor on body height in both genders. MA as well as BMC were found significantly higher in males than in females (p<0.0001 for both variables). We observed a significantly higher BMC/MA ratio in females than in males (p<0.0001). We found no effect either of the analyzed variables of gynecological history on bone/muscle characteristics. The findings highlight the necessity of involving height-adjusted parameters and BMC/MA ratio into bone analysis in adults.

Muscle mass during childhood--relationship to skeletal development.

Bone densitometric data often are difficult to interpret in children and adolescents because of large inter- and intraindividual variations in bone size. Here, we propose a functional approach to bone densitometry that addresses two questions: Is bone strength normally adapted to the largest physiological loads, that is, muscle force? Is muscle force adequate for body size? To implement this approach, forearm muscle cross-sectional area (CSA) and bone mineral content (BMC) of the radial diaphysis were measured in 349 healthy subjects from 6 to 19 years of age (183 girls), using peripheral quantitative computed tomography (pQCT). This functional approach to pediatric bone densitometric data should be adaptable to a variety of densitometric techniques.

24-h hydration status: parameters, epidemiology and recommendations.

Hydration of individuals and groups is characterised by comparing actual urine osmolality (Uosm) with maximum Uosm. Data of actual, maximum and minimum Uosm in infants, children and adults and its major influencing factors are reviewed. There are remarkable ontogenetic, individual and cultural differences in Uosm. In the foetus and the breast-fed infant Uosm is much lower than plasma osmolality, whereas in children and adults it is usually much higher. Individuals and groups may show long-term differences in Uosm. In industrialised countries, the gender difference of Uosm is common. There are large intercultural differences of mean 24-h Uosm ranging from 860 mosm/kg in Germany, 649 mosm/kg in USA to 392 mosm/kg in Poland. A new physiologically based concept called 'free-water reserve' quantifies differences in 24-h euhydration. In 189 boys of the DONALD Study aged 4.0-6.9 y, median urine volume was 497 ml/24-h and median Uosm 809 mosm/kg. Considering mean-2 s.d. of actual maximum 24-h Uosm of 830 mosm/kg as upper level of euhydration and physiological criterion of adequate hydration in these boys, median free-water reserve was 11 ml/24-h. Based on median total water intake of 1310 ml/24-h and the third percentile of free-water volume of -156 ml/24-h, adequate total water intake was 1466 ml/24-h or 1.01 ml/kcal. Data of Uosm in 24-h urine samples and corresponding free-water reserve values of homogeneous groups of healthy subjects from all over the world might be useful parameters in epidemiology to investigate the health effects of different levels of 24-h euhydration.

Gender-specific pubertal changes in volumetric cortical bone mineral density at the proximal radius.

It is well established that puberty affects the geometry of cortical bone differently in females and males. In the present study we investigated whether there are also gender differences in the volumetric bone mineral density of the cortical compartment (BMDcort). BMDcort was determined at the proximal radial diaphysis in 362 healthy children and adolescents (age 6-23 years; 185 females, 177 males) and in 107 adults (age 29-40 years; 88 women, 19 men) using peripheral quantitative computed tomography (pQCT). The densitometric result for BMDcort was similar in prepubertal girls and boys, but was significantly higher in females after pubertal stage 3. pQCT results for BMDcort are influenced by cortical thickness due to the partial volume effect. Therefore, these gender differences were reanalyzed in groups of subjects of the same developmental stage who were matched for cortical thickness. Thus calculated, no gender difference in BMDcort was detected in prepubertal children. However, adolescent females after pubertal stage 3 and adult women had a 3%-4% higher BMDcort than males at the same developmental stage. BMDcort is an integrated measure of both cortical porosity and mean material density of cortical bone. The metabolic activity of cortical bone (intracortical remodeling) increases cortical porosity and decreases the mean material density of cortical bone. Our results therefore suggest that intracortical remodeling is lower in postpubertal females than in males.

Influence of puberty on muscle development at the forearm.

Despite its fundamental importance for physical development, the growth of the muscle system has received relatively little consideration. In this study, we analyzed the relationship between cross-sectional area (CSA) of forearm muscles and maximal isometric grip force with age and pubertal stage. The study population comprised 366 children, adolescents, and young adults from 6 to 23 yr of age (185 female) and 107 adults (88 female) aged 29 to 40 yr. By use of peripheral quantitative computed tomography, muscle CSA was determined at the site of the forearm, whose distance to the ulnar styloid process corresponded to 65% of forearm length. Both muscle CSA and grip force were higher in prepubertal boys than in girls. The gender differences decreased until pubertal stage 3 and reincreased thereafter. In girls at pubertal stage 5, muscle CSA no longer increased with age (P > 0.4), whereas there was still some age-related increase in grip force (P = 0.02). In boys at pubertal stage 5, both muscle CSA and grip force continued to increase significantly with age (P < 0.005 each). Specific grip force (grip force per muscle CSA) adjusted for forearm length increased by almost one-half between 6 and 20 yr of age, with no difference between the genders. In conclusion, forearm muscle growth takes a gender-specific course during puberty, indicating that it is influenced by hormonal changes. However, the increase in specific grip force is similar in both genders and thus appears to be independent of sex hormones.

Renal excretion of calcium and phosphorus in premature infants with incipient late metabolic acidosis.

BACKGROUND: Premature infants receiving alimentation with cow milk-based formulas run a considerably high risk of incipient late metabolic acidosis, an early stage developing of manifest late metabolic acidosis. Is bone metabolism involved in pathophysiologic mechanisms characterizing this early stage of retention acidosis? METHODS: Urinary ionography was performed in 10 premature infants with spontaneous development of incipient late metabolic acidosis (indicated by urine pH < 5.4 on 2 consecutive days) and 10 pair-matched premature infants with normal values of urine pH; both groups were receiving full oral nutrition with the same standard formula. Moreover, in 37 premature infants with incipient late metabolic acidosis who were randomly allocated to oral therapy with 2 mmol. kg(-1). d(-1) of either NaHCO 3 or NaCl over a period of 7 days, urinary excretion of calcium and phosphorus was assessed on day 1 and day 7. RESULTS: Incipient late metabolic acidosis was accompanied by increased phosphaturia in premature infants receiving full oral nutrition. Seventeen premature infants receiving NaCl therapy (19 treatment periods) showed increased calciuria from day 1 to day 7, whereas, in 20 premature infants receiving NaHCO 3 therapy (23 treatment periods), calcium or phosphorus excretion in urine did not increase. CONCLUSIONS: The data of urinary calcium and phosphorus excretion in premature infants support the hypothesis that bone mineralization may already be impaired in the early stage of incipient late metabolic acidosis.

The midgrowth spurt in healthy children is not caused by adrenarche.

A small transient increase in growth, the midgrowth spurt, has been observed in several growth studies in healthy children around the age of 7 yr. During this time adrenarche (the physiological increase in adrenal androgen secretion) also occurs. Although it is now well established that estrogen, not androgen, has a critical role in the male (and female) pubertal growth spurt, a direct effect of androgens on growth cannot be excluded. In accordance with published observations that growth is frequently accelerated in infants and young children with late-diagnosed 21-hydroxylase deficiency (before adequate androgen suppression), it has been speculated that the adrenarchal increase in adrenal androgen secretion in healthy children could be responsible for the midgrowth spurt. To test this hypothesis we studied long-term serial changes in urinary 24-h excretion rates of dehydroepiandrosterone sulfate and total 17-ketosteroid sulfates in a group of healthy children (n = 12) in which yearly auxological measurements allowed the identification of a midgrowth spurt. Annual measurements of standing height were performed over periods of 6-9 yr before the onset of puberty. All children collected five to seven serial 24-h urine samples (1-yr intervals) each at the time of anthropometric examination. The peak of the midgrowth spurt was found to occur at a mean age of 6.8 +/- 1.0 yr. The average height of the midgrowth peak, i.e. average maximum gain in height velocity, was 0.9 cm/yr. In a peak-centered examination of individual 24-h excretion rates of dehydroepiandrosterone sulfate and 17-ketosteroid sulfates, primarily weak 1-yr changes in adrenal androgens were observed until the peak was attained. Only after the peak did increments in urinary adrenal androgen output become more pronounced. ANOVA performed on the peak-centered dehydroepiandrosterone sulfate and 17-ketosteroid sulfate excretion rates revealed a highly significant overall increase in adrenal androgen secretion from 2 yr before to 2 yr after the midgrowth spurt. After multiple testing, however, significant increments, when compared with the respective preceding androgen excretion levels, were for the first time seen 1 yr after the midgrowth spurt (dehydroepiandrosterone sulfate) or 2 yr later (17-ketosteroid sulfates). In conclusion, our longitudinal analysis of prepubertal growth and urinary adrenal androgen excretion in healthy children disproves the speculation that the midgrowth spurt is primarily caused by the adrenarchal increase in adrenal androgen secretion. However, the present results do not rule out a growth-accelerating effect of clearly higher androgen levels, as in premature adrenarche.

Representative data of iodine intake and urinary excretion in Germany.

To evaluate the iodine supply of the German population, 2500 representative subjects older than 13 years were elected for answering a specific food questionnaire. In addition spot urine samples in 3 selected risk groups for iodine deficiency (574 adults aged 50-70 years, 769 conscripts, 886 pairs of mothers and newborns) from 26 representative regions were collected. Furthermore the circadian iodine excretion was measured in 24 h urine samples collected in 6 fractions per day in 4 subgroups (young and older males and females) of 91 controls and this 24 h iodine excretion related to iodine/creatinine ratio in these subgroups. Mean estimated iodine intake was 119 microg/d in adults aged 50-70 years, 137 microg/d in conscripts, and 162 microg/d in mothers at still birth. The mean iodine concentration (iodine/creatinine ratio) was 9.4 microg/dl in 566 adults aged 50-70 years, 8.3 microg/dl in 772 conscripts and 5.6 microg/dl in 739 breast fed newborns. The mean daily iodine excretion was 134 microg/d in 278 men aged 50-70 years, 117 microg/d in 288 women aged 50-70 years, 125 microg/d in 772 conscripts and 74 microg/d in 53 breast-feeding mothers not using iodine tablets. These results show, that iodine intake in Germany has increased over the last years. The deficit in iodine intake with significant regional differences and defined risk groups for iodine deficiency (e.g. breast feeding mothers without iodine deficiency prophylaxis) is estimated to be about 30% of the recommended iodine intake.

The development of metaphyseal cortex--implications for distal radius fractures during growth.

Fractures of the distal radial metaphysis are very common in otherwise healthy children. The reasons for this high fracture incidence are not entirely clear. To address this problem, we undertook a detailed analysis of distal radius development using peripheral quantitative computed tomography (pQCT) at a site 4% proximal to the radial articular surface. The study population comprised 337 healthy children and adolescents (aged 6-18 years; 171 girls) and 107 adults (aged 29-40 years; 88 women). Total volumetric bone mineral density (vBMD) remained stable at about 70% of the adult value between the ages of 6-7 years and 14-15 years in both genders. Cortical thickness increased little between 6-7 years and 12-13 years in girls and 14-15 years in boys. Strength-Strain Index (SSI; a parameter combining geometry and density) was still at only 20% of the adult value in girls aged 10-11 years and at 21% of the adult level in boys aged 12-13 years. At these ages, factors that contribute to the mechanical challenge to the distal radius in case of a fall (forearm length and body weight) had already reached 49% and 36% of the adult value in girls and boys, respectively. The shaping of the distal radius cortex (metaphyseal inwaisting) was assessed by analyzing the decrease in cross-sectional bone size between adjacent bone slices in a separate population of 44 children (aged 8-19 years; 26 girls). The rates of periosteal resorption and endocortical apposition were estimated to average 8 microm/day and 10 microm/day, respectively, during the growth period. In conclusion, during growth the increase in distal radius strength lags behind the increase in mechanical challenges caused by a fall, because metaphyseal cortical thickness does not increase sufficiently. The endocortical apposition rate is already very high at that site and apparently cannot be further increased to levels that would be necessary to keep bone strength adapted to the mechanical requirements.

Changes in time-trends of nutrient intake from fortified and non-fortified food in German children and adolescents--15 year results of the DONALD study. Dortmund Nutritional and Anthropometric Longitudinally Designed Study.

BACKGROUND: Although fortified products have played an increasing role in food marketing since the 1980s in Germany, data as to the consumption of fortified food is sparse. AIM OF THE STUDY: To assess long-term data on changes in fortified food supply or consumption patterns, nutrient intake, and time trends in the DONALD Study (Dortmund Nutritional and Anthropometric Longitudinally Designed Study). METHODS: Between 1985 and 2000 consumption of nutrient intake (total and from fortified foods) was evaluated and time trends in energy and nutrient intake were assessed on the basis of 3-day weighed dietary records (n = 4193) of 2-14 year-old males (n = 383) and females (n = 404) enrolled in the DONALD Study. Nutrient intake was expressed as percentage of the current German recommendations. Food products were defined as fortified if enriched with at least one of the following nutrients: Vitamin A or provitamin A carotenoids (summarised as Vitamin A), Vitamins E, B1, B2, B6, C, niacin, folate, calcium or iron. Nutrient supplements and medicine were excluded from this evaluation. Time trends were analysed using linear and non-linear regression models (PROC MIXED, SAS 6.12). RESULTS: In percent of German references [3], non-fortified food contributed to folate intake by 20-30%, to Vitamin E by about 40%, to Vitamin B1 by 50-65%, to Vitamin A, C, B2, calcium, iron by about 65-95%, and to Vitamin B6 and niacin intake by 100% and more. Fortified food alone provided no more than 5% of calcium intake, about 10-20% of iron, Vitamin A and folate intake, up to 40-50% of Vitamin C, B1, B2, E, niacin and up to 80% of Vitamin B6 intake. During the 15 year period of the DONALD Study with total food, we only found a significant linear time trend for Vitamin C, whereas significant non-linear time trends were found for calcium, Vitamin E, B1, B2, B6, niacin and folate. In the latter there was a uniform increase until 1994 and a decrease thereafter. For iron and Vitamin A no significant time trend could be identified. Only iron and Vitamin A intake from fortified food showed a significant linear time trend. All other nutrients studied here gave significant non-linear time trends. Nutrient intake with fortified food reached maximum values between 1994 and 1996 followed by a decrease thereafter. CONCLUSIONS: Signs of changing food consumption patterns were found, pointing to an almost uniform decrease of nutrient intake since 1994/96 in our population of German children and adolescents. This could be an alarming indicator of a slight but unpreferable tendency to eat energydense, nutrient-poor foods.

Fifteen year trends in water intake in German children and adolescents: results of the DONALD Study. Dortmund Nutritional and Anthropometric Longitudinally Designed Study.

UNLABELLED: Water intake was evaluated and time trends in water intake and beverage consumption were assessed on the basis of 3 d weighed dietary records (n = 3,736) of 2-13-y-old males (n = 354) and females (n = 379) enrolled in the DONALD Study (Dortmund Nutritional and Anthropometric Longitudinally Designed Study, 1985-1999). Total water intake increased with age from 1,114 g d(-1) in the 2-3-y-olds to 1,363 g d(-1) in the 4-8-y-olds and further to 1,801 g d(-1) (1,676 g d(-1)) in the 9-13-y-old boys (girls); 33-38% came from food, 49-55% from beverages and 12-13% from oxidation. Total water intake per body weight decreased with age from 77.5 g kg(-1) (boys and girls) to 48.9 and 42.6 g kg(-1) in boys and girls, respectively. Milk (9-17%) and mineral water (12-15%) were the most important source of total water intake. In the 15 y period a significant increase in total water intake (+1.7 to +3.2 g MJ(-1) y(-1)) in all three age groups irrespective of sex was found. The increase of total water intake was mainly due to an increase in beverage consumption (+0.32 to +0.47% y(-1)). This study offers a differentiated insight into water intake and patterns of beverage consumption in German children and adolescents. CONCLUSION: The comparison of these data with other surveys points to a low total water intake, especially a low tap water intake, in German children and adolescents and underlines cultural influences on food and drinking habits.

Modeling of cross-sectional bone size, mass and geometry at the proximal radius: a study of normal bone development using peripheral quantitative computed tomography.

It is becoming increasingly accepted that bone size is an important determinant of bone mass. Studies on the development of bone size may therefore promote a better understanding of the basis of diseases which are due to low bone mass. Here, we characterize the temporal changes in cross-sectional bone size, geometry and mass at the radial diaphysis in healthy subjects from 6 to 40 years of age (n = 469; 273 females). Peripheral quantitative computed tomography was used to measure total and cortical cross-sectional area, bone mineral content (BMC) and volumetric bone mineral density (BMD) at the site of the forearm whose distance from the ulnar styloid process corresponded to 65% of forearm length. Over the age range of the study, total cross-sectional area increased by 39 mm2 (50%) in females and by 85 mm2 (116%) in males. Cortical area increased to a similar extent in both sexes. Between 6-7 years and adulthood, BMC increased by 52 mg/mm (111%) in females and by 73 mg/mm (140%) in males and was significantly higher in males after the age of 15 years. Volumetric BMD increased by 246 mg/cm3 (48%) in females but by only 132 mg/cm3 (23%) in males and was significantly higher in women than in men. In summary, these data show that BMC in men is higher than in women, because periosteal modeling continues longer in boys than in girls. Volumetric BMD is higher in women, partly because the size of the marrow cavity does not increase in girls as it does in boys.

Factors affecting renal hydrogen ion excretion capacity in healthy children.

In 560 healthy German children and adolescents aged 2.8-22.0 years from the DONALD (Dortmund Nutritional and Anthropometric Longitudinally Designed) study, the relationship between urine pH and renal net acid excretion (mmol/day/1.73 m2) was analysed. A quadratic model showed the best fit (r2 = 0.608). Using logistic regression analysis three parameters (urinary phosphorus excretion, total protein intake and urinary ratio of potassium and sodium) had a significant effect on renal hydrogen ion excretion capacity characterised by the probability of high or low net acid excretion with respect to the urine pH value. Urinary osmolality, in contrast to what has been seen in a previous experimental study with low birth weight infants, along with sex and age had no significant independent effects on renal net acid excretion with respect to the urine pH value over the range of osmolalities observed. In healthy children and adolescents a low fluid intake with high urinary osmolality does not at least substantially decrease the renal capacity of hydrogen ion excretion.

The foods most consumed by German children and adolescents: results of the DONALD Study. Dortmund Nutritional and Anthropometric Longitudinally Design.

BACKGROUND: For a successful nutrition counseling of children and adolescents, knowledge of dietary habits is mandatory. This report describes food group intake and gives details of the customary food selection of healthy German children and adolescents. Main foods which are consumed in large amounts were identified as those on which health promotion should be concentrated. METHODS: 3-day weighed dietary records of 344 children (age range 4-6 years) and 92 adolescents (age range 13-14 years) concerning the period 1990-1997 of the DONALD Study (Dortmund Nutritional and Anthropometric Longitudinally Designed Study) were evaluated. RESULTS: The number of different foods recorded during the 3-day observation period ranged from 21 to 70 and was independent of age or sex. In contrast to dietary guidelines, the consumption of animal foods and 'fats/oils' exceeded the consumption of plant foods with the exception of adolescent girls. Food selection was very similar in age and sex groups. CONCLUSION: Our study shows that under preventive aspects the current food selection could be improved without disturbing the prevailing dietary habits and food preferences.

Bone densities and bone size at the distal radius in healthy children and adolescents: a study using peripheral quantitative computed tomography.

Peripheral quantitative computed tomography (pQCT) has the ability to improve the diagnostic utility of densitometry in children and adolescents, because bone size and volumetric bone mineral density (vBMD) can be measured independently. Nevertheless, detailed reference data are lacking. We therefore performed pQCT (XCT-2000 scanner, Stratec, Inc., Pforzheim, Germany) at the distal radius in 371 healthy children, adolescents, and young adults (185 males and 186 females, ages 6-23 years) and in 107 of their parents (19 men and 88 women, ages 29-40 years). Total vBMD, trabecular, and "cortical + subcortical" vBMD as well as cross-sectional area (CSA) were determined at the "4% site" of the distal radius. This location was defined as the site whose distance to the most distal portion of the growth plate or to the radial articular surface corresponded to 4% of the forearm length. In both genders, total vBMD remained stable between 6 and 15 years of age and then increased by 30% in girls and by 46% in boys. Regarding pubertal development, total vBMD remained almost constant throughout pubertal stages 1-4 and thereafter increased in both genders. Trabecular vBMD did not change with age in girls, whereas in boys an increase with age of about 10% was noted after 15 years of age. Males had higher trabecular vBMD than females. This gender difference increased from 6% in prepubertal children to 23% in adults. The variation with age and pubertal stage in "cortical + subcortical" vBMD-cort was similar to that of total vBMD. CSA roughly doubled between 6 and 15 years of age in both genders. In conclusion, the availability of this reference material will provide a basis for the use of pQCT in the assessment of pediatric bone diseases.

The development of bone strength at the proximal radius during childhood and adolescence.

Current investigations of bone development mostly focus on bone mass, but bone strength may be functionally more important than mass. Therefore, we compared the developmental changes in cortical bone mass (BMCcort) and parameters of cortical bone strength [polar moment of inertia, section modulus, and strength strain index (SSI)]. Analyses were performed at the 65% site of the proximal radius using peripheral quantitative computed tomography. The study population comprised 469 healthy subjects, 6-40 yr of age (273 females). Both in prepubertal children (pubertal stage 1) and after puberty (pubertal stage 5 and adults) all studied parameters were significantly higher in males. During puberty (pubertal stages 2-4) the gender-specific differences were generally somewhat smaller. All of the measured parameters increased significantly with age and pubertal stage. However, although the percent increase in BMCcort between the youngest children and adults was similar between the genders, the increases in polar moment of inertia, section modulus, and SSI were higher in males. The ratio between section modulus and BMCcort was consistently higher in males after the age of 11 yr and after pubertal stage 2. Similar results were found for ratios between polar moment of inertia or SSI and BMCcort. These results show that for a given bone mass, males have stronger bones than females after pubertal stage 2. This reflects the fact that in puberty males add bone mostly on the periosteal surface, where the effect on bone strength is highest, whereas females add bone on the endocortical surface, which has a small effect on bone stability. The purpose of the mechanically inefficient endocortical apposition in female puberty might be to create a reservoir of calcium for future pregnancy and lactation.

History of nutrition and acid-base physiology.

In the 17th century the notion of nutrition and diet changed in northern European countries. First chemical experiments fostered the idea that salts resulted from a union of acids and bases. Digestion was no more regarded as a process of cooking but a succession of fermentations controlled by a balanced production of acids and alkali. Life seemed to depend on the equilibrium of acids and alkalis. In the 19th century food was systematically analysed for the content of energy and macronutrients and first scientifically based nutritional standards were formulated. The preferred use of processed food from the new food industry resulted in epidemics of nutritional disorders. Acidosis seemed to be a plausible pathogenic factor. Practitioners (S Ishizuka, H Hay, FX Mayr) formulated holistic doctrines integrating the concept of balance of acids and bases and recommending food with an excess of alkali. New micromethods to determine the concentration of electrolytes and blood acid-base status promoted physiological and clinical research into acid-base metabolism in the 1960s. In the new physiologically based terminology of systemic acid-base status, the relationship between blood acid-base status and net acid intake or excretion was, however, incorrectly simplified. In the 1970s metabolic acidosis was observed in patients on chemically defined diets and parenteral nutrition. Based on the data of comprehensive acid-base balance studies, calculation models were used to estimate renal net acid excretion from nutrient intake and to predict the potential renal acid load of single foods. Extrapolating current trends to the future, one can say that acid-base physiology will probably remain a challenge in nutrition and functional medicine over the next few years. The challenge will include new concepts for the manipulation of nutritional acid load in sports, dietetics and preventive medicine as well as new definitions of the upper intake level of potential renal acid load in functional foods and the monitoring of renal net acid excretion in populations.